Kustomize vs Helm

In this article, we’ll compare Helm and Kustomize—two popular methods for managing Kubernetes manifests across different environments. Understanding their strengths, workflows, and trade-offs will help you select the best fit for your project.

How Helm Works: Go-Templating in YAML

Helm uses Go templates to inject dynamic values into your Kubernetes manifests. Placeholders in the form of {{ .Values.variable }} are replaced at deploy time based on a values.yaml file.

# templates/nginx-deployment.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  name: {{ .Values.name }}
spec:
  replicas: {{ .Values.replicaCount }}
  selector:
    matchLabels:
      app: {{ .Values.name }}
  template:
    metadata:
      labels:
        app: {{ .Values.name }}
    spec:
      containers:
        - name: {{ .Chart.Name }}
          image: "nginx:{{ .Values.image.tag }}"

# values.yaml
replicaCount: 1
image:
  tag: "2.4.4"
name: "my-app"

When you run helm install my-app ./chart -f values.yaml, Helm merges the values into the templates, producing valid Kubernetes YAML:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: my-app
spec:
  replicas: 1
  selector:
    matchLabels:
      app: my-app
  template:
    metadata:
      labels:
        app: my-app
    spec:
      containers:
        - name: my-chart
          image: "nginx:2.4.4"

Use --values (or -f) to specify different environment files, e.g., -f values.prod.yaml.

Helm Chart Structure

A typical Helm chart directory might look like:

k8s/
├── environments/
│   ├── values.dev.yaml
│   ├── values.stg.yaml
│   └── values.prod.yaml
└── templates/
    ├── nginx-deployment.yaml
    ├── nginx-service.yaml
    ├── db-deployment.yaml
    └── db-service.yaml

templates/: Kubernetes manifests with Go templating syntax.
environments/: Separate values.*.yaml files for each environment.

Feature Comparison

Feature	Helm	Kustomize
Template Syntax	Go templates (`{{ }}`)	Pure YAML overlays and patches
Conditional Logic & Loops	✔️ Supports `if`, `range`, custom functions	❌ Not supported
Packaging & Versioning	✔️ Full-fledged chart packaging, dependencies, hooks	❌ No built-in packaging
Valid YAML Before Rendering	❌ Not valid until `helm template` runs	✔️ Always valid YAML
Native Kubernetes Integration	✔️ Widely adopted, independent CLI	✔️ Built into `kubectl`

Complex Helm charts with extensive logic can become hard to read and maintain. Ensure you document templates and values clearly.

Trade-offs: When to Use Each Tool

Use Helm if
• You need advanced templating (conditionals, loops, custom functions)
• You want packaging, versioning, and chart dependencies
• You require lifecycle hooks (e.g., pre-install, post-upgrade)
Use Kustomize if
• You prefer pure YAML without an extra rendering step
• You want easy-to-read overlays and patches
• Your customization needs are straightforward (e.g., changing images, labels)

Balance your project’s complexity and team familiarity when choosing between the two.

The image is a slide comparing Kustomize and Helm, highlighting Helm's features such as being a package manager, providing conditionals, loops, functions, and hooks, and noting that Helm templates are not valid YAML due to Go templating syntax.

Introduction

Kustomize Basics

Secret/Config Generator

Other Commands

Kustomize Overview

Capstone Project

How Helm Works: Go-Templating in YAML

Helm Chart Structure

Feature Comparison

Trade-offs: When to Use Each Tool

References

Watch Video

​How Helm Works: Go-Templating in YAML

​Helm Chart Structure

​Feature Comparison

​Trade-offs: When to Use Each Tool

​References

Watch Video

How Helm Works: Go-Templating in YAML

Helm Chart Structure

Feature Comparison

Trade-offs: When to Use Each Tool

References